#1 - Proteins - structure and function relationship and transportation Flashcards
What are the key characteristics of globular proteins?
Globe-like shape
High solubility in water
Examples: enzymes, signaling proteins, antibodies, transporters
What are fibrous proteins and their characteristics?
Rod-like shape
Low solubility in water
Involved in structural functions
Examples: tropomyosin, myosin (muscle tissue), elastin (skin, lungs), fibrin (silk, spider webs), keratin, collagen
What determines protein structure and function?
Primary structure: sequence of amino acids
Unique sequence leads to a unique folded structure (native conformation)
Native conformation determines protein function
What are hydrophobic amino acids?
Glycine, Alanine, Valine, Cysteine, Proline
What are polar charged amino acids and their characteristics?
Lysine, Arginine, Histidine (amino groups form ionic interactions)
Aspartic acid, Glutamic acid (negatively charged due to carboxylate groups)
Where is keratin found and what is its structure?
Found in feathers, beaks, nails, claws, hair, skin
Forms dimers with α-helical structure (3.5 residues per turn)
Tandem repeats of 7 residues, with hydrophobic 1st and 4th residues
What are polar uncharged amino acids?
]Serine, Threonine, Tyrosine
What is the primary structure of collagen?
Repeating tripeptide pattern (GLY - X - Y)
X is often proline, Y is often hydroxyproline
Glycine appears every third position
What is the structure of keratin intermediate filaments
Heterodimers form anti-parallel tetramers
Elongate into non-polar protofilaments, bundling into 10 nm intermediate filaments
Where is collagen found and its significance?
Found in bones, teeth, muscles, cornea, skin, connective tissues
30% of total protein mass is collagen
Extremely strong: 1mm can support 10 kg
How do disulfide bonds contribute to keratin structure?
Cysteine residues form disulfide bonds between keratin dimers
Stabilize keratin filaments with strong covalent bonds
What is the secondary structure of collagen?
Polyproline type II helix (3 residues per turn)
No H-bonds, stabilized by steric repulsion of proline rings
What type of helix forms the collagen triple helix?
Each monomer is a polyproline type II helix
Triple helix is stabilized by H-bonds between hydroxyproline and glycine (every third position)
What is Type I collagen and where is it found?
90% of the body’s collagen
Dense, provides structure to skin, bones, tendons
Forms fibrils stabilized by covalent cross-links (lysines and hydroxylysines)
What is Type IV collagen and its role?
Found in the basement membrane of skin
Non-helical regions and globular domains for flexibility
Forms a branched network
